I just did a Fedora Rawhide installation in a VM which has kernel
5.16.0-0.rc3.20211201git58e1100fdc59.25.fc36.x86_64

The installation depends on loop mounted squashfs image as the source,
and rsync as the copy mechanism. In top I see quite a few high CPU
btrfs-delalloc as well, more than expected. I'll redo the installation
and see if there were any deadlock warnings or anything like that, and
if not I'll grab sysrq+t during the heavier btrfs CPU usage.

The guest uses virtio drives; and the host uses NVMe.

--
Chris Murphy